title: NADPH oxidase and nitric oxide synthase-dependent superoxide production is increased in proliferative lupus nephritis.
abstract: OBJECTIVE
  Lupus nephritis (LN) is an immune complex-mediated glomerulonephritis. Proliferative LN (PLN, ISN/RPS classes III and IV)) often leads to renal injury or failure despite traditional induction and maintenance therapy. Successful targeted therapeutic development requires insight into mediators of inflammation in PLN. Superoxide (SO) and its metabolites are mediators of the innate immune response through their ability to mediate reduction-oxidation signaling. Endothelial nitric oxide synthase (eNOS) modulates inflammatory responses in endothelial cells. We hypothesized that markers of SO production would be increased in active PLN and that SO production would be dependent on the activity of select enzymes in the renal cortex.
  
  
  METHODS
  Patients with systemic lupus erythematosus were enrolled at the time of renal biopsy for active LN of all classes. Serum collected at baseline was analyzed by HPLC with electrochemical detection for markers of SO production (durable modifications of serum protein Tyr ultimately requiring SO as a substrate). Renal cortex from MRL/MpJ-FAS(lpr) (MRL/lpr) mice with and without functional eNOS was analyzed during active disease for superoxide (SO) production with and without inhibitors of SO-producing enzymes.
  
  
  RESULTS
  Serum protein modifications indicative of total SO production were significantly higher in patients with PLN. These markers were increased in association with more active, inflammatory PLN. Mice lacking functional eNOS had 80% higher levels of renal cortical SO during active disease, and inhibitors of nitric oxide synthase and NADPH oxidase reduced these levels by 60% and 77%, respectively.
  
  
  CONCLUSIONS
  These studies demonstrate that SO production is unique to active PLN in a NOS and NADPH oxidase-dependent fashion. These findings suggest the emulating or augmenting eNOS activity or inhibiting NADPH oxidase SO production may be targets of therapy in patients with PLN. The markers of SO production used in this study could rationally be used to select SO-modulating therapies and serve as pharmacodynamic indicators for dose titration.
authors.affiliation: 1Department of Medicine, Division of Rheumatology, Medical University of South Carolina, Charleston, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Oates
authors.forename: A K
authors.initials: AK
authors.lastname: Mashmoushi
authors.forename: S R
authors.initials: SR
authors.lastname: Shaftman
authors.forename: G S
authors.initials: GS
authors.lastname: Gilkeson
mesh_terms: D000328:Adult; D000818:Animals; D001706:Biopsy; D001798:Blood Proteins / Q000378:metabolism; D049109:Cell Proliferation; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D007672:Kidney Cortex / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D008181:Lupus Nephritis / Q000097:blood / Q000201:enzymology* / Q000473:pathology; D008297:Male; D051379:Mice; D019463:Mice, Inbred MRL lpr; D018345:Mice, Knockout; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011446:Prospective Studies; D013481:Superoxides / Q000097:blood / Q000378:metabolism*; D014443:Tyrosine; D015854:Up-Regulation; D055815:Young Adult
chemical_list: D001798:Blood Proteins; D004791:Enzyme Inhibitors; D013481:Superoxides; D014443:Tyrosine; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019255:NADPH Oxidases
keywords: Lupus nephritis; NADPH oxidase; endothelial nitric oxide synthase; inflammation; nitric oxide; oxidation–reduction; proliferative lupus nephritis; superoxide; systemic lupus erythematosus